The site software has an interesting habit of displaying our images larger than 1:1 - it seems to be about 1.7:1 or 2:1. I have a 4K monitor that is 2300 pixels tall and when I edit in PS Adobe always shows them to me as 1:1 with the screen pixels so 1100 pixels tall occupies less than 1/2 of height of my screen. When I upload it to the site and bring the image up it fills the screen height and I almost have to scroll to see all of it. I made a few images taller than 1100 pixels and Jim kept complaining he could never see all of the image so I now size my portrait mode web images to no more than 1100 pixels on the vertical side.
There is a size limit for directly uploaded images that I think is still set to 1200 pixels wide and anything larger than that gets resampled down to 1200 pixels. There is no similar mechanism for the vertical dimension so no resizing is in effect until you reach 1200 pixels wide which will make for a lot of scrolling with a portrait image.